Partial exchange transfusion is used in sickle cell anemia when surgery is indicated, when life-threatening complications (for example bilobar pneumonia) occur, or when a patient is totally incapacitated from recurrent crises. Because stored blood has reduced 2,3-DPG (thus, high oxygen affinity) and since the oxygen affinity of sickle cell blood is low, infusion of large amounts of stored blood could cause dramatic alteration of the recipient's blood oxygen affinity. The present study has indicated that when frozen, washed, packed cells were used, oxygen affinity of the recipient's blood remained reduced for at least 24 hours after transfusion, even when a 75% exchange is achieved. We believe that this procedure significantly improves oxygen transport and reduces the risk of tissue hypoxia immediately after the transfusion.